CVE-2025-25224: Luxcal Web Calendar Info Disclosure Flaw

CVE-2025-25224 Overview

CVE-2025-25224 is a missing authentication vulnerability affecting the LuxCal Web Calendar application. The vulnerability exists in the dloader.php file, which fails to properly verify user authentication before processing file download requests. This authentication bypass allows unauthenticated attackers to retrieve arbitrary files from the server, potentially exposing sensitive configuration files, database contents, and other confidential data.

Critical Impact
Unauthenticated attackers can remotely access and download arbitrary files from servers running vulnerable versions of LuxCal Web Calendar, leading to potential exposure of sensitive data including configuration files, credentials, and database information.

Affected Products

LuxCal Web Calendar prior to version 5.3.3M (MySQL version)
LuxCal Web Calendar prior to version 5.3.3L (SQLite version)

Discovery Timeline

2025-02-18 - CVE-2025-25224 published to NVD
2025-09-15 - Last updated in NVD database

Technical Details for CVE-2025-25224

Vulnerability Analysis

This vulnerability is classified as CWE-306 (Missing Authentication for Critical Function). The dloader.php script in LuxCal Web Calendar is designed to handle file download operations but lacks proper authentication checks before serving file requests. This design flaw allows unauthenticated remote attackers to craft requests that retrieve files from the server filesystem.

The attack can be executed remotely over the network without requiring any user interaction or prior authentication. Successful exploitation results in unauthorized access to sensitive file contents on the server, though the vulnerability does not directly allow file modification or system disruption.

Root Cause

The root cause of this vulnerability is the absence of authentication verification in the dloader.php file handler. The script processes incoming requests and serves files without first validating that the requesting user has appropriate permissions or is authenticated to the calendar application. This represents a fundamental access control failure where a critical function (file retrieval) lacks necessary security gates.

Attack Vector

The vulnerability is exploitable through direct network requests to the dloader.php endpoint. An attacker can craft HTTP requests targeting this script with parameters designed to specify arbitrary files on the server. Since no authentication is required, the attacker can enumerate and retrieve files accessible to the web server process.

The attack surface includes:

Direct HTTP/HTTPS requests to the vulnerable endpoint
No user interaction required for exploitation
No authentication credentials needed
Files accessible by the web server process can potentially be retrieved

Successful exploitation could expose configuration files containing database credentials, application secrets, user data exports, and other sensitive information stored on the server.

Detection Methods for CVE-2025-25224

Indicators of Compromise

Unusual or unauthorized HTTP requests targeting dloader.php with suspicious file path parameters
Web server logs showing repeated requests to dloader.php from external IP addresses
Access attempts to sensitive file paths through the download handler (e.g., configuration files, database files)
Unexpected outbound data transfers following requests to the vulnerable endpoint

Detection Strategies

Monitor web server access logs for requests to dloader.php containing path traversal sequences (e.g., ../)
Implement Web Application Firewall (WAF) rules to detect and block file inclusion attack patterns
Configure file integrity monitoring for sensitive configuration and data files
Deploy intrusion detection systems with signatures for authentication bypass attempts

Monitoring Recommendations

Enable detailed logging on web servers hosting LuxCal Web Calendar installations
Set up alerts for access to dloader.php from untrusted IP addresses
Monitor for anomalous file access patterns that may indicate reconnaissance or data exfiltration
Review access logs periodically for signs of exploitation attempts

How to Mitigate CVE-2025-25224

Immediate Actions Required

Upgrade LuxCal Web Calendar to version 5.3.3M or later for MySQL installations
Upgrade LuxCal Web Calendar to version 5.3.3L or later for SQLite installations
Review web server logs for signs of prior exploitation attempts
Audit any files that may have been accessed through the vulnerable endpoint

Patch Information

Luxsoft has released patched versions of LuxCal Web Calendar that address this vulnerability. Organizations should download the appropriate patched version from the Luxsoft Download Page. Additional details about the security fix can be found in the Luxsoft Forum Discussion. The official vulnerability report is available at the JVN Vulnerability Report.

Workarounds

Restrict access to dloader.php using web server configuration (e.g., IP whitelisting or HTTP authentication)
Implement additional authentication checks at the web server or reverse proxy level
Consider temporarily removing or renaming the dloader.php file if the download functionality is not critical
Place the LuxCal Web Calendar installation behind a VPN or restricted network segment

bash

# Example Apache configuration to restrict access to dloader.php
<Files "dloader.php">
    Require ip 192.168.1.0/24
    # Or require authentication
    # AuthType Basic
    # AuthName "Restricted Access"
    # AuthUserFile /path/to/.htpasswd
    # Require valid-user
</Files>